1). Field of the Invention
This invention relates to a capacitor structure that is included in a substrate of an integrated circuit package.
2). Discussion of Related Art
Integrated circuits are usually manufactured on wafer substrates. Wafer substrate is then “diced” or “singulated” into individual dies, each die carrying a respective integrated circuit. The die is then mounted on a package substrate, often with an intermediate interposer substrate. The substrate or substrates provide structural rigidity to the resulting integrated circuit package. A package substrate also provides x-y transformation from contacts of the die to contacts on a carrier substrate on which the integrated circuit package is mounted.
Signals can be provided through conductors in the substrate or substrates to and from an integrated circuit in the die. Signal delay, referred to as resistance-capacitance-inductance delay, often occurs when signals are transmitted through the conductors. In order to reduce resistance-capacitance-inductance delay, a capacitor is often provided close to the die. The capacitor acts as a reservoir of power close to the integrated circuit.
Discrete capacitors are relatively large and thus take up a large amount of real estate on a substrate. It has been appreciated that thin film capacitors may take up less real estate, which will allow for more capacitors to be formed. It may also be simpler to manufacture thin film capacitors during the manufacture of a substrate than to mount discrete capacitors to a substrate.
Via openings have to be manufactured in a base structure of a substrate, in which conductive vias have to be formed to which power and ground planes of a thin film capacitor structure have to be connected. The formation of such via openings has been a preoccupation of the semiconductor industry for a number of years. Thus far, all efforts have been directed to drilling openings in low k-value materials such as silicon. Silicon is a brittle material, which makes it difficult to drill openings therein. Each opening also has to be drilled individually, which reduces throughput.